The purpose of the proposed research project will be to study the mechanism of intercellular communication (beat synchronization) between mouse myocardial cells in culture, and to study how the generation of this phenomenon is related to the biogenesis of the low-resistance intercellular junction, the gap junction or nexus. In order to study biogenesis, information will first be obtained by utilizing subcellular fractionation techniques to isolate an enriched fraction of gap junctions from rat liver and myocardium. The isolated junctions will be characterized ultrastructurally, biochemically and immunologically in order to obtain information about endogenous components, and their contribution to the phenomenon of communication. Simultaneously, cultured mouse neonatal ventricular cells will be examined electrophysiologically and morphologically for cell-to-cell communication (beat synchronization). With information from previous procedures, the relationship of generation of intercellular conduction (beat synchronization) to the biogenesis of the gap junction will be studied. Further, the recognition events leading to the establishment of junctional interaction will be studied by applying junction-specific antisera and components with known cell surface specificities to the myocardial cells in culture prior to interaction.